These kinds of potentiometric FET-sensors are suited for measuring the pH value or the redox potential of an analyte. DE 198 57 953 C2 concerns, for example, the realization of a pH-ISFET-sensor, in which, for reducing the circuit complexity, the ISFET-sensor is connected in a bridge circuit having at least three additional resistances. Regarding the mounting of the FET-sensor, the following principles are, among others, known. Benton discloses in U.S. Pat. No. 5,833,824 a pH-sensor, in which an ISFET-chip is secured on the underside of a substrate by means of a metal seal, which surrounds the ion-sensitive region of the ISFET-chip, with the ion-sensitive region being aligned with an opening in the substrate. Outside of the region surrounded by the seal, conductive traces on the surface of the chip are directed to contact areas, which are connected via solder, braze or weld connections with complementary contact areas on the underside of the substrate. The solution proposed by Benton is very complex, to the extent that, both in the case of the manufacture of the seal and also in the case of the implementation of the electrical contacting, involved solder, braze, or weld processes are required. $The state of the art discussed in Benton describes ISFET-sensors, in which an ordinary polymer seal is arranged about the opening of the sample chamber wall between the substrate and the ion-sensitive region of the ISFET-chip. The contacting of the ISFET-chip occurs, however, not to the substrate in the sense of Benton, but, instead, to a carrier, which supports the ISFET-chip on the rear side facing away from the substrate. For this purpose, bond wires are led between contact areas on the front side of the ISFET-chip to contact areas on the carrier outside of the bearing surface of the ISFET-chip. Also, this solution is complicated, because bonding tasks are required for contacting the chip, and because, for assuring function and integrity of the sensor, the chip must be oriented within narrow tolerances, both with reference to the substrate and with reference to the carrier. $Additionally, solutions are known, in which the chips have their contact areas, or bonding pads, on the rear side facing away from the ion-sensitive region. These chips can then be contacted on the rear side via a carrier having complementary contact areas, with an anisotropic, elastic conductor, e.g. a silicone foil with embedded gold threads, being arranged in a direction perpendicular to the plane of the foil, for assuring adequate galvanic contact between the rear side of the chip and the carrier. These solutions are very expensive hi-the with respect that to the leading of the electrical contacts through the chip from its front side to its rear side1 makes making its manufacturing costs a number of times greater.
In the unpublished German Patent Application No. 10260961.6 of the assignee of the present application, a sensor arrangement is disclosed having a single ISFET-, or CHEMFET-, sensor with a front-side mounting by means of an anisotropic conductor.